Cooling in high-temperature environments can be addressed in a variety of ways. A particular cooling technique can be chosen based upon a variety of context-dependent factors such as, for example, the degree of cooling that needs to take place, the type of structure to be cooled and its geometry, and the operational environment and its various working parameters. Internal heat pipes and refrigerant or cryogenic fluid circulation represent two commonly used cooling techniques. Forced air or compressed gas flow over a surface is another common technique for heat dissipation. In some instances, ablation of a sacrificial heat shield can be an effective strategy for thermal protection of a surface.
The foregoing heat dissipation techniques can be problematic in various aspects, particularly for high-performance applications such as air and space vehicles. Internal cooling systems such as heat pipes and refrigerant circulators can add significantly to an air or space vehicle's weight, thereby diminishing its operational performance and payload-carrying capabilities. Further, the geometry of narrow aerodynamic leading edge structures (e.g., nose cones and wing tips), stagnation regions (e.g., scramjet inlets and equipment stores), and flow diverters (e.g., control surfaces and added surface roughness areas to induce turbulent transition) in such vehicles can make it difficult to provide effective cooling with internal cooling systems. In general, an aircraft's performance-to-loss ratio (e.g., lift-to-drag or thrust-to-drag) is defined by the sharpness of its leading edges. Accordingly, cooling can be a particular issue during hypersonic flight due to the sharpness of the leading edges.
Forced air or compressed gas cooling can be used for dissipation of heat from turbine blades, for example, but such cooling mechanisms can considerably increase the complexity of engine design and decrease operational performance. Ablation strategies can often represent a successful approach, particularly for atmospheric reentry applications, but this technique likewise has its limitations. In situations where a part's shape is critical to its performance, ablative heat shields are generally not a suitable approach, since the part's exterior surface changes its shape upon ablation. This can be an issue for leading edges and similar aircraft structures. Ablative heat shields may also need to be refurbished between heating cycles. Under severe thermal loads, ablative heat shields and other types of active cooling mechanisms also can saturate and not provide a desired degree of thermal protection. Finally, ablative heat shields are most effectively applied to blunt surfaces and can considerably add to a vehicle's weight, thereby impacting its operational performance and payload-carrying capabilities. The narrow geometry of aerodynamic leading edges, in contrast, makes these structures much more difficult to protect with ablative heat shields.
In view of the foregoing, advanced techniques and materials for thermal dissipation in high-performance environments would be of significant interest in the art. The present disclosure satisfies these needs and provides related advantages as well.